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Subsonic Flow Over

a Missile Configuration

Subsonic flowfields over a missile airframe at 45 degree roll angle and 10 degree canard deflection were computed at 15, 30 degree 45 and 60 degree incidence angles. The flowfield is assumed to be symmetric across the mid-span plane and the computational domain is discretized by structured, overset grids. A total number of 1.68 million grid points are employed to discretize the missile body, two canards, two gap regions between the canard and the body, and two tails. The grids were generated by Dr. Ekaterinaris in the earlier stages of the project. The OVERFLOW Navier-Stokes solver developed in NASA-Ames is used for the numerical solution. The flowfield is assumed to be fully turbulent and the Baldwin-Lomax algebraic turbulence model is employed. The steady flowfields are computed at a free stream Mach Number of 0.3, and a Reynolds Number of 950000 which is based on the diameter of the missile body.

The computed flowfields are given in terms of surface pressure distributions ( 15, 30, 45, 45a, 45b, 60 ), particle traces and helicity contours ( 15, 30, 45, 60 ), and surface streamlines ( 15, 30, 45, 60 ). At 45 degree incidence, the Mach number contours show that the flow separates massively as the canard and the body vortices merge on the lee-ward side as opposed to the attached flow over the missile and the distinct canard vortices in the wake at 15 degree incidence. The Mach number contours in the flow direction behind the canards show the wake of the canard vortices and the body vortices formed downstream of the mid-missile length. Since only the grids around the close vicinity of the missile is used in producing the contour plots, the computational domain away from the missile body which are not covered with these grids are cut out and appear in black. The computed normal force and the pitching moment about the center of gravity located at 11.45 diameter distance downstream from the nose are compared against the experimental data and missile DATCOM predictions. Up to 30 degree incidence, the agreement is excellent. Although the normal force is under-predicted at higher incidences, the flattening trend in both the normal force and moment coefficients is captured. At high angles of attack, the unsteadiness of the flowfield and asymmetric vortex shedding may need to be considered.

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